Three dedicated ports instead of daisy-chaining—that's the wiring philosophy behind Shimano's BT-DN300 battery. Each derailleur gets its own direct connection to the power source, which simplifies the cable routing inside your frame and makes troubleshooting easier if something goes wrong down the line. The battery fits inside seat posts or down tubes using the same mounting hardware as the previous BT-DN110, so swapping from an older 12-speed Di2 setup is straightforward if your frame already accommodates internal batteries. Fixing hardware comes included for standard installations.

The BT-DN300 works exclusively with Shimano's thinner SD300 wiring, which arrived alongside the R9200 Dura-Ace and R8100 Ultegra generations. If you're building up a new Di2 system or replacing a battery on an existing 12-speed setup, this is the correct unit. It won't work with the older SD50 wires from 11-speed Di2 systems—those require the BT-DN110 or external mount batteries instead. Compatibility extends across the full 12-speed Di2 range including Dura-Ace, Ultegra, 105, and GRX components that use the SD300 wire standard.

Shimano rates the lithium-ion cell at approximately 1000 to 2000 kilometers per charge depending on how often you use the front derailleur, which consumes more power than rear shifts. Riders running 1x setups or those who spend most of their time in the big ring will land toward the higher end of that range. Charging happens through the rear derailleur itself using the EW-EC300 cable, which connects to any USB-A power source. A full charge takes roughly 90 minutes from a wall adapter or up to 3 hours from a computer's USB port. The E-Tube Project app monitors charge level and handles firmware updates, and you can check battery status directly through any compatible Di2 display or junction.... Read More